Remember how the new "knowledge engine" WolframAlpha said it was ready for 175 million queries a day at launch? It turns out the service and its supercomputer-backed infrastructure hasn't performed well in traffic load tests, and this evening's scheduled soft launch (the official launch is Monday) could be delayed, according to the LA Times.UPDATE: The WolframAlpha team went ahead with a live "launch" broadcast, but was about three hours late with its scheduled kickoff as the WA team battled a logging database and latency between two colo sites. By 11 pm Eastern time the WolframAlpha site was live and responding to queries.

Here's an excerpt of comments to the LAT from Stephen Wolfram, the creator of WolframAlpha: "We have several supercomputer-class compute clusters," Wolfram said. "One of our tests was to use one cluster to simulate traffic and run it against the other cluster. And when we did that last night, we found that the through-put we got degraded horribly when we increased the amount of traffic that we were pushing from one cluster to the other. So we don’t quite understand that, and that would very much degrade the through-put that we could get."

The Wolfram team later updated its blog, announcing its intent to launch as planned but acknowledging the scalability challenges:

"One of the biggest challenges we’re navigating today is effectively linking our supercomputers together," the WA team wrote. "We’ve been switching on more and more compute capacity, with the expectation of having full capacity available on Monday. Tonight, we’re looking to begin to test the system on a larger scale, get a sense of how it will behave, and continue performance tuning."

WolframAlpha will run on infrastructure spread across five data centers, and be able to handle 175 million queries a day at launch, the company said in a blog post this week. Wolfram’s computing horsepower includes “two supercomputers, just about 10,000 processor cores, hundreds of terabytes of disks, a heck of a lot of bandwidth, and what seems like enough air conditioning for the Sahara to host a ski resort,” the company said.